Climate change, so what? Implications for ground movement and landslide event frequency in the Ventnor Undercliff, Isle of Wight

The town of Ventnor is located on the south coast of the Isle of Wight in an area of ancient coastal landslides known as the Undercliff. The ancient landslide complex is marginally stable and has been subject to ground movement and occasional landslide events in some locations causing significant damage to property and infrastructure. Since 1992, the local authority has made a significant investment in real-time monitoring and analysis of hydrogeological data at key sites, which has considerably advanced understanding about the relationships between climate and ground behaviour response. These data reveal close relationships between antecedent rainfall conditions, groundwater levels and ground movement rates, confirming that prolonged periods of heavy rainfall and associated elevated groundwater levels are a fundamental trigger of ground movement and landslide events. Latest climate change predictions point to significant increases in winter rainfall frequency, intensity and amount, drier summers and rising sea level which are likely to prove particularly challenging in terms of managing ground instability in the Undercliff. The implications of climate change predictions for the Undercliff are both spatial and temporal; firstly, there are concerns that hitherto marginally stable areas of the Undercliff may become unstable due to reactivation of ground movement and the occurrence of new landslides, secondly, in areas previously affected by ground movement or landslides, the frequency and rate of ground movement and landsliding is expected to increase. The paper presents historical and contemporary data to demonstrate the relationships between rainfall and ground movement and uses these to project the likely impacts of climate change predictions on the future stability of the Undercliff. The paper concludes that climate change poses a very real and significant challenge to the future management of the Undercliff and other similarly marginally stable ancient landslides in southern Britain.